Researchers led by Francois Sztark at the University of Bordeaux in southwestern France analysed data from a long-term study into cognitive decline covering 9,300 elderly people in three French cities.
The volunteers — average age 75 — were interviewed when they were recruited into the study and then two, four, seven and 10 years afterwards.
The data showed a link between the onset of dementia and a general anaesthetic that had been administered two or three years before.
Those who had received general anaesthesia were 35 percent likelier to develop dementia symptoms by the next follow-up interview compared with counterparts who had not had general anaesthetic.
Previous work has already highlighted a condition called post-operative cognitive dysfunction, or POCD, in which an elderly patient who undergoes major surgery also goes into mental decline relatively soon afterwards.
The reasons for this, though, are unclear. Some experiments suggest that various anaesthetics inflame neural tissues, causing protein plaques and tangles to develop that are precursors of Alzheimer's disease.
The research was released at a congress in Barcelona, Spain, of the European Society of Anaesthesiology.
"These results are in favour of an increased risk for dementia several years after general anaesthesia," Sztark said in a press release, adding that patients who underwent major surgery needed long-term support.